This invention relates to a means for mitigating the effects of a coolant loop pipe rupture in a nuclear reactor. More specifically, this invention relates to a means of preventing rapid loss of liquid coolant from the core of a nuclear reactor in the event of a ruptured pipe in a coolant loop. The invention also relates to a means for retaining molten core material in the vessel of a nuclear reactor.
In a typical nuclear reactor design, fissile fuel is contained in a reactor core which is housed in a reactor vessel. During nuclear fission, the fuel in the core produces large quantities of heat which can be used to generate electricity in a power plant. A flowing coolant is used to transfer the heat from the reactor core to the electric power plant. In nuclear reactors cooled by a flowing liquid in which the liquid is circulated by several coolant loops, a rupture or failure of one of the loops may result in the loss of coolant from the reactor core. The core may then overheat and melt, causing extensive damage to both the core and vessel. Thus, a device to mitigate the effects of a coolant loop rupture would maintain coolant flow in the core region for as long a time as possible. This would be accomplished by increasing the pressure drop from the core region to the ruptured coolant loop. An appropriate form of such a device could also retain any molten core debris and 10 spread it over a large area to promote rapid cooling.
Various devices have been suggested to minimize the reversed flow of coolant through the inlet pipe of a failed coolant loop. Such devices are passive and operate on the basics of fluidics, such as the vortex diode. These devices reduce the reversed flow of coolant but they do not provide a structure for retention of molten core debris or for spreading the debris over a large area. In current reactor designs, the debris retention capability of the lower head of the reactor is limited by the curvature of the vessel. In addition, the debris bed may be too thick to cool without remelting.